With regard to cigarettes, it is imperative to understand that the absorptive capacity of the lungs is hundreds of times greater than the tissue in the mouth. Thus, far more nicotine is passed into the bloodstream when smoke is inhaled. When cigarette smoke is taken into the lungs, it deposits 80% of the tars into the respiratory tract and passes 90% of the nicotine directly into the bloodstream. Within seconds of each inhalation, nicotine-sensitive receptors in the brain activate neurotransmitters which cause the release of enzymes. These enzymes quickly increase heart rate, raise blood pressure, constrict blood vessels, and produce other reactions which create a mildly narcotic effect on the user. Consequently, the lung-specific delivery method and concentration of nicotine, coupled with the instantaneous effects of inhalation, are what make cigarette smoking a potentially compulsive and/or addictive behavior. This potent, nearly instantaneous cigarette “high” is profoundly different from the experience of cigar and pipe smokers who absorb nicotine through their mouth, not the lungs.